1. Field of the Invention
The present invention relates generally to systems for monitoring a medical patient's exhalation and more specifically to a media filter which separates the moisture from the gases of the exhalation in anticipation of gas analysis or measurement.
2. Discussion of the Prior Art
In the course of medical treatment, it is often desirable to monitor a patient's exhalation and sometimes measure and analyze the gases. Analysis of the gases require that the exhalation be free from moisture which is contained in the exhalation. The removal of moisture is accomplished by a moisture filter.
There are two types of moisture filters on the market today, the first being a chamber type and the second being a media type. Simply stated, the chamber type has an inlet, an outlet and a chamber. The gases pass through the inlet, moisture collects in the chamber and the moisture free gases pass through the outlet into a monitoring system for analysis. The media type has an inlet, an outlet and a filtering material. The gases pass through the inlet into a filtering material, the filtering material traps or retains the moisture from the gases and the moisture free gases pass through the outlet into a monitoring system for analysis. The present invention is a media type moisture filter. The following descriptions are two media type moisture filters that have been disclosed in recent years.
In U.S. Pat. No. 4,446,869, Knodle discloses a media type filter in which a patient's exhalations pass through a cylindrical chamber in a moisture absorbing material. Moisture in the gases is absorbed by the moisture absorbing material. A pellet filter at the outlet of the moisture absorbing material prevents passage of gases through the outlet by swelling with moisture if the moisture absorbing material becomes substantially saturated with moisture.
In U.S. Pat. No. 5,131,387, French et al. discloses a media type filter in which a patient's exhalations pass through a hydrophilic material contained in a housing. A side passage in the housing allows a moisture absorbing material to wick off moisture contained in the hydrophilic material. A pellet filter at the outlet of the hydrophilic material prevents passage of the gases if the moisture absorbing material becomes substantially saturated with moisture. The pellet filter, being of a microporous hydrophobic material will not allow passage of condensed moisture.
Both these filters have common shortcomings. First, there is no indication given when the filter becomes saturated with moisture. When saturation of the filter occurs, an alarm will sound requiring possible emergency response from the caregiver. Second, some of the exhalation gases will be absorbed by the moisture absorbing material in addition to moisture which renders a less accurate reading of the gases present in the patient's exhalation.
Accordingly, there is a clearly felt need in the art for a media filter which gives an indication when the filter is becoming substantially saturated with moisture. There is also a need for an improvement to the moisture absorbing material which more thoroughly blocks the moisture absorbing material from absorbing gases of the patient's exhalation. There is also a need for a media filter which is simpler and has fewer parts than the prior art. These unresolved problems are clearly felt in the art and are solved by the disclosed invention in the manner described below.